The invention involves addition of material to a surface to ease the topography and provide ramps and chamfered edges to features that originally have steep, vertical or undercut faces. For example, surface mount electronic components placed on a printed circuit board may have facet heights of several hundred microns or more and these facets would usually present themselves as vertical walls substantially at 90 degrees to the plane of the board. Many techniques exist which apply coatings by depositing liquids from above the substrate; these include liquid dispensing, spray coating and inkjet printing. In such a situation, these techniques would have great difficulty in reliably coating the vertical wall of such a component in order to provide a continuous coating across the board and whole component.
Our co-pending International Patent Application No. PCT/GB2004/004595 (WO 2005/044451) describes the deposition of an adhesive substance around a silicon chip in order to overcome a vertical edge and allow a second material to be inkjet printed continuously from the substrate up to a contact pad located on the top surface of the silicon chip. WO 2005/044451 gives the example of using a high speed glue dispenser to dispense drops of adhesive on either side of the chip in order to build up a ramp of material.
Although this is an adequate solution it requires a degree of control and accuracy which would render it a relatively slow step in a continuous production process.